EP3642941A1 - An electric machine - Google Patents

An electric machine

Info

Publication number
EP3642941A1
EP3642941A1 EP18722182.5A EP18722182A EP3642941A1 EP 3642941 A1 EP3642941 A1 EP 3642941A1 EP 18722182 A EP18722182 A EP 18722182A EP 3642941 A1 EP3642941 A1 EP 3642941A1
Authority
EP
European Patent Office
Prior art keywords
bearing
electric machine
support body
rotor assembly
adhesive
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP18722182.5A
Other languages
German (de)
French (fr)
Inventor
Christopher Sullivan
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Dyson Technology Ltd
Original Assignee
Dyson Technology Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Dyson Technology Ltd filed Critical Dyson Technology Ltd
Publication of EP3642941A1 publication Critical patent/EP3642941A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K5/00—Casings; Enclosures; Supports
    • H02K5/04—Casings or enclosures characterised by the shape, form or construction thereof
    • H02K5/16—Means for supporting bearings, e.g. insulating supports or means for fitting bearings in the bearing-shields
    • H02K5/161—Means for supporting bearings, e.g. insulating supports or means for fitting bearings in the bearing-shields radially supporting the rotary shaft at both ends of the rotor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D25/00—Pumping installations or systems
    • F04D25/02—Units comprising pumps and their driving means
    • F04D25/06—Units comprising pumps and their driving means the pump being electrically driven
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D25/00—Pumping installations or systems
    • F04D25/02—Units comprising pumps and their driving means
    • F04D25/026—Units comprising pumps and their driving means with a magnetic coupling
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/04—Shafts or bearings, or assemblies thereof
    • F04D29/043—Shafts
    • F04D29/044—Arrangements for joining or assembling shafts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/05—Shafts or bearings, or assemblies thereof, specially adapted for elastic fluid pumps
    • F04D29/056—Bearings
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/08—Sealings
    • F04D29/10—Shaft sealings
    • F04D29/12—Shaft sealings using sealing-rings
    • F04D29/122—Shaft sealings using sealing-rings especially adapted for elastic fluid pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/26—Rotors specially for elastic fluids
    • F04D29/266—Rotors specially for elastic fluids mounting compressor rotors on shafts
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K1/00—Details of the magnetic circuit
    • H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
    • H02K1/12—Stationary parts of the magnetic circuit
    • H02K1/18—Means for mounting or fastening magnetic stationary parts on to, or to, the stator structures
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K1/00—Details of the magnetic circuit
    • H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
    • H02K1/22—Rotating parts of the magnetic circuit
    • H02K1/27—Rotor cores with permanent magnets
    • H02K1/2706—Inner rotors
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K5/00—Casings; Enclosures; Supports
    • H02K5/04—Casings or enclosures characterised by the shape, form or construction thereof
    • H02K5/16—Means for supporting bearings, e.g. insulating supports or means for fitting bearings in the bearing-shields
    • H02K5/173—Means for supporting bearings, e.g. insulating supports or means for fitting bearings in the bearing-shields using bearings with rolling contact, e.g. ball bearings
    • H02K5/1732—Means for supporting bearings, e.g. insulating supports or means for fitting bearings in the bearing-shields using bearings with rolling contact, e.g. ball bearings radially supporting the rotary shaft at both ends of the rotor
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
    • H02K7/003—Couplings; Details of shafts
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
    • H02K7/08—Structural association with bearings
    • H02K7/083—Structural association with bearings radially supporting the rotary shaft at both ends of the rotor
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
    • H02K7/14—Structural association with mechanical loads, e.g. with hand-held machine tools or fans
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/26—Rotors specially for elastic fluids
    • F04D29/28—Rotors specially for elastic fluids for centrifugal or helico-centrifugal pumps for radial-flow or helico-centrifugal pumps
    • F04D29/284—Rotors specially for elastic fluids for centrifugal or helico-centrifugal pumps for radial-flow or helico-centrifugal pumps for compressors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2240/00—Components
    • F05D2240/50—Bearings
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2240/00—Components
    • F05D2240/60—Shafts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C27/00—Elastic or yielding bearings or bearing supports, for exclusively rotary movement
    • F16C27/06—Elastic or yielding bearings or bearing supports, for exclusively rotary movement by means of parts of rubber or like materials
    • F16C27/066—Ball or roller bearings
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
    • H02K7/04—Balancing means
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
    • H02K7/14—Structural association with mechanical loads, e.g. with hand-held machine tools or fans
    • H02K7/16—Structural association with mechanical loads, e.g. with hand-held machine tools or fans for operation above the critical speed of vibration of the rotating parts

Definitions

  • the present invention relates to an electric machine.
  • electric machines such as brushless electric motors
  • improvements may be desired in terms of size weight, manufacturing cost, efficiency, reliability and noise.
  • This invention provides an electric machine comprising: a stator assembly; a rotor assembly; and a support body.
  • the rotor assembly comprises a shaft to which is mounted a first bearing and a second bearing either side of a permanent magnet
  • the support body comprises first and second bearing seats to which the bearings of the rotor assembly are mounted, wherein the first bearing is mounted to the first bearing seat by adhesive, and the second bearing is soft-mounted to the second bearing seat by an o-ring.
  • the shaft may be driving a load mounted to one end of the shaft, and the second bearing may be closer to the load than the first bearing.
  • the bearing that is closest to the load is soft mounted to the support body. Radial forces are most likely to be generated by the load attached to the shaft, and so it is beneficial for the bearing closest to the load to be able to absorb any radial forces caused by the load spinning during use so that it does not have a negative impact on the strength of the adhesive bond at the other bearing. Any axial forces are transferred along the rotor assembly, and are withstood by the bearing which is spaced further away from the load.
  • the electric machine may be a compressor and the load may be an impeller.
  • the impeller may be a mixed flow impeller.
  • An annular groove may be provided in at least one of the outer surface of the second bearing and the bearing seat, and the o-ring is positioned in said annular groove.
  • An annular groove may be provided in at least one of the outer surface of the first bearing, and the bearing seat, the annular groove providing a channel in which adhesive can be located.
  • This channel can allow for a clean adhesive bond, and reduces the chance that adhesive will flow out from between the bearing and the bearing seat during assembly which would reduce the effectiveness of the adhesive bond. If adhesive was able to flow out, there is also the chance that it may enter into the bearing itself which would be extremely detrimental to the bearing and could stop it from functioning completely.
  • the support body may comprise an elongate central part, and the first and second bearing seats may be positioned axially at opposite ends of the elongate central part such that the permanent magnet is positioned within the elongate central part of the support body.
  • the elongate central part may support the stator assembly.
  • Figure 1 shows an exploded perspective view of a compressor
  • Figure 2 shows an exploded perspective view of a rotor assembly
  • Figure 3 shows an assembled rotor assembly
  • Figure 4 shows a cross section of a compressor
  • Figure 1 shows an exploded perspective view of an electric machine 10 in the form of a compressor. Certain components, such as control electronics and an external housing, are not shown for clarity.
  • the electric machine 10 includes a rotor assembly 12, a support body 14 and a stator assembly comprising four stator elements 16, 18, 20 and 22.
  • the rotor assembly 12 is located within and mounted to the support body 14, and the stator elements are located in respective slots in the support body 14.
  • the stator element 20 is located within slot 24 in the support body.
  • the support body 14 may be a one-piece construction, for example moulded as a single object, and includes an impeller shroud 26 that covers the impeller as shown in Figure 4.
  • the motor 10 also includes a diffuser 28.
  • FIG. 2 shows an exploded perspective view of the rotor assembly 12.
  • the rotor assembly 12 comprises a shaft 30 on which is mounted a rotor core permanent magnet 32, a first balancing ring 34 and a second balancing ring 36.
  • a pair of bearings 38, 40 are mounted on the shaft 30 on either side of the core 32 and balancing rings 34, 36.
  • An impeller is 42 is mounted at one end of the shaft 30, and a sensor magnet 44 is mounted at the other end.
  • Figure 3 shows an assembled rotor assembly 12. Similar to Figure 2, the rotor assembly 12 comprises a shaft 30 on which is mounted a rotor core permanent magnet 32, and balancing rings 34, 36 positioned either side of the magnet 32. At one end of the magnet 32, fixed to the shaft 30 is a first bearing 40 with is provided with an annular groove or channel 41 on the outer circumferential surface thereof. The groove 41 provides a channel in which adhesive can be located. When the rotor assembly 12 is assembled into place within the support body 14, the first bearing 40 sits inside a bearing seat in the support body, and is fixed therein using adhesive.
  • the channel 41 allows for a stronger bond to be achieved between the first bearing 41 and the bearing seat, and reduces the chance that adhesive will flow out from between the bearing and the bearing seat during assembly which would reduce the effectiveness of the adhesive bond. Furthermore, if adhesive was able to flow out, there would be a chance that adhesive may contaminate the bearing itself which would be extremely detrimental to the bearing and could stop it from functioning completely.
  • Fixed to the shaft 30 at the opposite end of the magnet 32 is a second bearing 38.
  • An o-ring 39 is placed around the second bearing 38.
  • the second bearing is also is provided with an annular groove or channel (not shown) on the outer circumferential surface thereof.
  • the o-ring 39 sits within this channel in order that the o-ring remains in a desired position on the bearing 38 and will not move around.
  • the second bearing 38 sits inside a second bearing seat in the support body, and is soft mounted thereto by way of the o-ring 39.
  • Figure 4 shows a cross-section of the assembled electric machine 10 through a plane that includes the axis of rotation of the rotor assembly 12.
  • the stator elements 16, 20 are shown inserted into their respective slots in the support body 14, for example stator element 20 is inserted into slot 24.
  • the bearings 38, 40 of the rotor assembly 12 are positioned within the support body 14 and mounted to bearing seats 50 and 52 respectively.
  • bearing 38 is soft- mounted within bearing seat 50 by an o-ring
  • bearing 40 is hard mounted to bearing seat 52 by adhesive.
  • the first bearing 40 is positioned further away from the impeller 42 than the second bearing 38.
  • the first bearing 40 is fixed to the bearing seat 52 by adhesive, and is able to withstand axial forces along the rotor that are generated by the impeller 42 during use.
  • the second bearing 38 is positioned within the bearing seat 50 closest to the impeller 42. Because the second bearing 38 is only soft mounted within the bearing seat 50 by way of the o-ring, it is able to absorb any radial forces generated by the impeller 42 as it spins during use. If an adhesive bond had been used to fix bearing 38 to bearing seat 50, then it is possible that radial forces could have weakened the adhesive bond over time, reducing the life of the motor, and potentially resulting in a catastrophic failure of the electric machine 10.
  • the soft mounting cannot withstand any axial forces generated along the rotor assembly by the impeller during use, which is why an adhesive bond is used to fix the other bearing 40 to the bearing seat 52, and the use of two different mounting methods for each of the bearings is so beneficial.
  • annular channel provided in the outer surface of each of the bearings may be provided on the inner surface of the bearing seat of the support body instead.
  • the embodiments shown and described herein are directed to a compressor with an impeller.
  • the invention would be beneficial to other types of electric machine such as brushless electric motors used to drive loads other than impellers.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Structures Of Non-Positive Displacement Pumps (AREA)
  • Connection Of Motors, Electrical Generators, Mechanical Devices, And The Like (AREA)
  • Motor Or Generator Frames (AREA)
  • Permanent Field Magnets Of Synchronous Machinery (AREA)

Abstract

An electric machine comprising: a stator assembly; a rotor assembly; and a support body. The rotor assembly comprises a shaft to which is mounted a first bearing and a second bearing either side of a permanent magnet, and the support body comprises first and second bearing seats to which the bearings of the rotor assembly are mounted, wherein the first bearing is mounted to the first bearing seat by adhesive, and the second bearing is soft-mounted to the second bearing seat by an o-ring.

Description

An Electric Machine
The present invention relates to an electric machine. There is a general desire to improve electric machines, such as brushless electric motors, in a number of ways. In particular, improvements may be desired in terms of size weight, manufacturing cost, efficiency, reliability and noise.
It is becoming more and more common for electric machines such as brushless electric motors to be used a very high speeds, for example at l OOkrpm or more. When operating at such high speeds, the components of the motor are subjected to very large forces. In order for the motor to maintain performance and reliability over the lifetime of the motor, it must be capable of withstanding these large forces. Therefore, there is a need to find improvements that allow motors to withstand large forces experienced at high operating speeds.
This invention provides an electric machine comprising: a stator assembly; a rotor assembly; and a support body. The rotor assembly comprises a shaft to which is mounted a first bearing and a second bearing either side of a permanent magnet, and the support body comprises first and second bearing seats to which the bearings of the rotor assembly are mounted, wherein the first bearing is mounted to the first bearing seat by adhesive, and the second bearing is soft-mounted to the second bearing seat by an o-ring. As a result, the rotor assembly, and the points of connection between the rotor assembly and the support body, can more effectively withstand and absorb both axial and radial forces that they are subjected to when the electric machine is in use. The bearing which is soft mounted is effective at absorbing radial forces, and the bearing which is fixed by adhesive is effective at withstanding any axial forces. As such, a beneficial synergistic effect arises from the use of two different mounting methods for the two bearings.
The shaft may be driving a load mounted to one end of the shaft, and the second bearing may be closer to the load than the first bearing. As a result, the bearing that is closest to the load is soft mounted to the support body. Radial forces are most likely to be generated by the load attached to the shaft, and so it is beneficial for the bearing closest to the load to be able to absorb any radial forces caused by the load spinning during use so that it does not have a negative impact on the strength of the adhesive bond at the other bearing. Any axial forces are transferred along the rotor assembly, and are withstood by the bearing which is spaced further away from the load.
The electric machine may be a compressor and the load may be an impeller. The impeller may be a mixed flow impeller.
An annular groove may be provided in at least one of the outer surface of the second bearing and the bearing seat, and the o-ring is positioned in said annular groove. As a result, the o-ring will remain in the desired position and will not shift position which could reduce the effectiveness of the soft mounting provided by the o-ring.
An annular groove may be provided in at least one of the outer surface of the first bearing, and the bearing seat, the annular groove providing a channel in which adhesive can be located. This channel can allow for a clean adhesive bond, and reduces the chance that adhesive will flow out from between the bearing and the bearing seat during assembly which would reduce the effectiveness of the adhesive bond. If adhesive was able to flow out, there is also the chance that it may enter into the bearing itself which would be extremely detrimental to the bearing and could stop it from functioning completely. The support body may comprise an elongate central part, and the first and second bearing seats may be positioned axially at opposite ends of the elongate central part such that the permanent magnet is positioned within the elongate central part of the support body. The elongate central part may support the stator assembly. As a result, very tight control of the relative positioning of the magnet and the stator assembly can be achieved, which may result in a more efficient electric machine.
In order that the present invention may be more readily understood, embodiments of the invention will now be described, by way of example, with reference to the following accompanying drawings, in which: Figure 1 shows an exploded perspective view of a compressor; Figure 2 shows an exploded perspective view of a rotor assembly;
Figure 3 shows an assembled rotor assembly; and Figure 4 shows a cross section of a compressor. Figure 1 shows an exploded perspective view of an electric machine 10 in the form of a compressor. Certain components, such as control electronics and an external housing, are not shown for clarity. The electric machine 10 includes a rotor assembly 12, a support body 14 and a stator assembly comprising four stator elements 16, 18, 20 and 22. When the electric machine 10 is assembled, the rotor assembly 12 is located within and mounted to the support body 14, and the stator elements are located in respective slots in the support body 14. For example, the stator element 20 is located within slot 24 in the support body. The support body 14 may be a one-piece construction, for example moulded as a single object, and includes an impeller shroud 26 that covers the impeller as shown in Figure 4. The motor 10 also includes a diffuser 28.
Figure 2 shows an exploded perspective view of the rotor assembly 12. The rotor assembly 12 comprises a shaft 30 on which is mounted a rotor core permanent magnet 32, a first balancing ring 34 and a second balancing ring 36. When the rotor assembly 12 is assembled, a pair of bearings 38, 40 are mounted on the shaft 30 on either side of the core 32 and balancing rings 34, 36. An impeller is 42 is mounted at one end of the shaft 30, and a sensor magnet 44 is mounted at the other end.
Figure 3 shows an assembled rotor assembly 12. Similar to Figure 2, the rotor assembly 12 comprises a shaft 30 on which is mounted a rotor core permanent magnet 32, and balancing rings 34, 36 positioned either side of the magnet 32. At one end of the magnet 32, fixed to the shaft 30 is a first bearing 40 with is provided with an annular groove or channel 41 on the outer circumferential surface thereof. The groove 41 provides a channel in which adhesive can be located. When the rotor assembly 12 is assembled into place within the support body 14, the first bearing 40 sits inside a bearing seat in the support body, and is fixed therein using adhesive. The channel 41 allows for a stronger bond to be achieved between the first bearing 41 and the bearing seat, and reduces the chance that adhesive will flow out from between the bearing and the bearing seat during assembly which would reduce the effectiveness of the adhesive bond. Furthermore, if adhesive was able to flow out, there would be a chance that adhesive may contaminate the bearing itself which would be extremely detrimental to the bearing and could stop it from functioning completely. Fixed to the shaft 30 at the opposite end of the magnet 32 is a second bearing 38. An o-ring 39 is placed around the second bearing 38. Although it can't be seen in Figure 3, the second bearing is also is provided with an annular groove or channel (not shown) on the outer circumferential surface thereof. The o-ring 39 sits within this channel in order that the o-ring remains in a desired position on the bearing 38 and will not move around. When the rotor assembly 12 is assembled into place within the support body 14, the second bearing 38 sits inside a second bearing seat in the support body, and is soft mounted thereto by way of the o-ring 39.
Figure 4 shows a cross-section of the assembled electric machine 10 through a plane that includes the axis of rotation of the rotor assembly 12. The stator elements 16, 20 are shown inserted into their respective slots in the support body 14, for example stator element 20 is inserted into slot 24. It can also be seen that the bearings 38, 40 of the rotor assembly 12 are positioned within the support body 14 and mounted to bearing seats 50 and 52 respectively. Although not shown in Figure 4, bearing 38 is soft- mounted within bearing seat 50 by an o-ring, and bearing 40 is hard mounted to bearing seat 52 by adhesive.
The first bearing 40 is positioned further away from the impeller 42 than the second bearing 38. The first bearing 40 is fixed to the bearing seat 52 by adhesive, and is able to withstand axial forces along the rotor that are generated by the impeller 42 during use. The second bearing 38 is positioned within the bearing seat 50 closest to the impeller 42. Because the second bearing 38 is only soft mounted within the bearing seat 50 by way of the o-ring, it is able to absorb any radial forces generated by the impeller 42 as it spins during use. If an adhesive bond had been used to fix bearing 38 to bearing seat 50, then it is possible that radial forces could have weakened the adhesive bond over time, reducing the life of the motor, and potentially resulting in a catastrophic failure of the electric machine 10. However, the soft mounting cannot withstand any axial forces generated along the rotor assembly by the impeller during use, which is why an adhesive bond is used to fix the other bearing 40 to the bearing seat 52, and the use of two different mounting methods for each of the bearings is so beneficial.
Whilst particular embodiments have thus far been described, it will be understood that various modifications may be made without departing from the scope of the invention as defined by the claims. For example, the annular channel provided in the outer surface of each of the bearings may be provided on the inner surface of the bearing seat of the support body instead. In addition, the embodiments shown and described herein are directed to a compressor with an impeller. However, the invention would be beneficial to other types of electric machine such as brushless electric motors used to drive loads other than impellers.

Claims

An electric machine comprising:
a stator assembly;
a rotor assembly; and
a support body;
the rotor assembly comprising a shaft to which is mounted a first bearing and a second bearing either side of a permanent magnet, and the support body comprising first and second bearing seats to which the bearings of the rotor assembly are mounted,
wherein the first bearing is mounted to the first bearing seat by adhesive, and the second bearing is soft-mounted to the second bearing seat by an o-ring.
An electric machine as claimed in claim 1 , wherein the shaft is driving a load mounted to one end of the shaft, and the second bearing is closer to the load than the first bearing.
An electric machine as claimed in claim 2, wherein the electric machine is a compressor and the load is an impeller.
An electric machine as claimed in claim 3, wherein the impeller is a mixed flow impeller.
An electric machine as claimed in any one of the preceding claims, wherein an annular groove is provided in at least one of the outer surface of the second bearing and the bearing seat, and the o-ring is positioned in said annular groove.
An electric machine as claimed in any one of the preceding claims, wherein an annular groove is provided in at least one of the outer surface of the first bearing, and the bearing seat, the annular groove providing a channel in which adhesive can be located.
7. An electric machine as claimed in any one of the preceding claims, wherein the support body comprises an elongate central part, and the first and second bearing seats are positioned axially at opposite ends of the elongate central part, such that the permanent magnet is positioned within the elongate central part of the support body.
8. An electric machine as claimed in claim 7, wherein the elongate central part supports the stator assembly.
EP18722182.5A 2017-06-20 2018-04-27 An electric machine Withdrawn EP3642941A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB1709839.3A GB2563617B (en) 2017-06-20 2017-06-20 An electric machine
PCT/GB2018/051134 WO2018234739A1 (en) 2017-06-20 2018-04-27 An electric machine

Publications (1)

Publication Number Publication Date
EP3642941A1 true EP3642941A1 (en) 2020-04-29

Family

ID=59462335

Family Applications (1)

Application Number Title Priority Date Filing Date
EP18722182.5A Withdrawn EP3642941A1 (en) 2017-06-20 2018-04-27 An electric machine

Country Status (8)

Country Link
US (2) US11300130B2 (en)
EP (1) EP3642941A1 (en)
JP (1) JP6689318B2 (en)
KR (1) KR102281734B1 (en)
CN (2) CN208623466U (en)
GB (1) GB2563617B (en)
TW (1) TW201906283A (en)
WO (1) WO2018234739A1 (en)

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